An assay substrate is a surface upon which various chemical and/or biological analyses can be performed. Examples of an assay substrate include microarray plates, glass slides, and microtiter plates. A microtiter plate (also known as multiwell plate) is a plate that has multiple “wells” formed in its surface. Each well can be used as a small test tube into which various materials can be placed to perform biochemical analyses. One illustrative use of microtiter plates includes for conducting biochemical assays such as an enzyme-linked immunosorbent assay (ELISA), which is a modern medical diagnostic testing technique.
Multiwell plates are commonly used for biological research applications, particularly cellular and/or biochemical assays. Such assays or techniques may be conducted with high throughput, as multiwell plates commonly contain 96 or more separate wells where individual experiments may be conducted. After an assay is performed, an amount of residual material may be left in the wells. One technique for removing the residual material is to do so manually. Because various individuals may be performing the same task at different timepoints in the assay, even slight differences in how each individual may process the plate introduces inconsistent assay results, especially in highly sensitive assays. Contamination between wells may also occur throughout the wash process, compromising signal intensity and resulting in a need to run additional replicates of the same samples.
Another technique for removing residual material is to use plate washers that aspirate the residual material from the wells. For example, fluid is dispensed and aspirated by lowering twin sets of aspirate and dispense tubes from the top of the well plate multiple times. However, these automated plate washers have several disadvantages. For example, the aspirate needles often do not eliminate all of the residual material in the wells, compromising the wash process. Additionally, while this technique may be generally effective for the first few rounds of aspirating and dispensing, subsequent aspirations with the same tubes may contaminate the samples. Furthermore, aspirating and dispensing with twin sets of tubes is a time-consuming process.
Using another technique, a plate washer utilizes centripetal forces to expel the fluid from the wells. This technique does not use aspirate needles but also has several disadvantages. For example, this technique also expels the well's fluid onto the inner walls of the wash instrument, creating the potential for cross contamination of subsequently processed assay plates.
Because of the disadvantages of the current techniques for washing plates, a need exists for systems and methods to provide consistent washing of multiwell plates used for biochemical assays and techniques.